Avalon VT 737 sp

[TheseGoToEleven]

just tested again, nope no readings on 63 or 64 whatsoever even when cranking up gain and output and t12 readin 13, no readings on 63&64

To be clear, you measured 13 volts AC at T12, but had no reading at 64?

just saw that on the tube card c5 and c4 are flipped upside down, never touched these ones, is this normal?

These capacitors are not polarized so it doesn't matter.

 

[punkt]

To be clear, you measured 13 volts AC at T12, but had no reading at 64?


These capacitors are not polarized so it doesn't matter.

exactly i turned gain and output on max andmeasured 13 ACV on t12 but nothing on 64 or 63

 

[TheseGoToEleven]

exactly i turned gain and output on max andmeasured 13 ACV on t12 but nothing on 64 or 63

If you turn off the unit, can you set the output knob to "0db" and measure the resistance between 63 and 64? And show a picture of the meter while you are doing it? The black probe should be plugged into "COM" on your meter, the red probe should be plugged in the right side (V-ohm-mA), and the meter should be set to "200k". Sorry if this is super basic but in an earlier pic you were measuring with one probe on the left and one on the right and nothing in "COM". So I just want to make sure.

 

[punkt]

If you turn off the unit, can you set the output knob to "0db" and measure the resistance between 63 and 64? And show a picture of the meter while you are doing it? The black probe should be plugged into "COM" on your meter, the red probe should be plugged in the right side (V-ohm-mA), and the meter should be set to "200k". Sorry if this is super basic but in an earlier pic you were measuring with one probe on the left and one on the right and nothing in "COM". So I just want to make sure.

done i get 9,5

 

[TheseGoToEleven]

done i get 9,5

Ok, that looks good. With the output knob at "0db", the resistance should measure about the same as between 63 and 62. I think we tested this before. It means your output knob is ok.

 

[punkt]

Ok, that looks good. With the output knob at "0db", the resistance should measure about the same as between 63 and 62. I think we tested this before. It means your output knob is ok.

whats next on the list to check/replace?

 

[TheseGoToEleven]

With the unit off, can you measure the resistance between T12 and 64?

 

[punkt]

With the unit off, can you measure the resistance between T12 and 64?

jup 71,2

 

[TheseGoToEleven]

jup 71

Ok, what setting was the meter on? 200k?

 

[punkt]

Ok, what setting was the meter on? 200k?

yes

 

[TheseGoToEleven]

Ok so that would mean 71k ohms between T12 and 64. It should really be close to zero. Between T12 and 64 there are 4 relays to examine. You will have to flip the unit over and measure resistance from the bottom side.

With the 200k setting, please measure:
Resistance between pins 2 & 3 on relay K7.
Resistance between pins 8 & 9 on relay K7.
Resistance between pins 2 & 3 on relay K8.
Resistance between pins 8 & 9 on relay K8.
Resistance between pins 2 & 3 on relay K9.
Resistance between pins 8 & 9 on relay K9.
Resistance between pins 2 & 3 on relay K12.
Resistance between pins 8 & 9 on relay K12.

From the bottom, the relay pins look like this:

 

[punkt]

Ok so that would mean 71k ohms between T12 and 64. It should really be close to zero. Between T12 and 64 there are 4 relays to examine. You will have to flip the unit over and measure resistance from the bottom side.

With the 200k setting, please measure:
Resistance between pins 2 & 3 on relay K7.
Resistance between pins 8 & 9 on relay K7.
Resistance between pins 2 & 3 on relay K8.
Resistance between pins 8 & 9 on relay K8.
Resistance between pins 2 & 3 on relay K9.
Resistance between pins 8 & 9 on relay K9.
Resistance between pins 2 & 3 on relay K12.
Resistance between pins 8 & 9 on relay K12.

From the bottom, the relay pins look like this:
View attachment 147230

k7 118/118
k8 0/no reading
k9 no reading/0
k12 118/118

 

[TheseGoToEleven]

k7 118/118
k8 0/no reading
k9 no reading/0
k12 118/118

Ok, the unit was turned off, right? If so, then it looks like relays K7 and K12 are not working properly. All of those readings should be zero when the unit is turned off. My advice would be to replace K7 and K12.

Pucho would you agree?

Any of the other relays might malfunction sometimes too, or they might be fine. This can happen with age, dirt, overheating, etc. So replace K7 and K12 for sure. I would also replace relay K2 since you said there was sometimes unwanted noise when you use the "Phase" button. You can replace more relays if you want to. They are all the same.

The relays are Panasonic TQ2-12V, part number ATQ203.

 

[punkt]

Ok, the unit was turned off, right? If so, then it looks like relays K7 and K12 are not working properly. All of those readings should be zero when the unit is turned off. My advice would be to replace K7 and K12.

Pucho would you agree?

Any of the other relays might malfunction sometimes too, or they might be fine. This can happen with age, dirt, overheating, etc. So replace K7 and K12 for sure. I would also replace relay K2 since you said there was sometimes unwanted noise when you use the "Phase" button. You can replace more relays if you want to. They are all the same.

The relays are Panasonic TQ2-12V, part number ATQ203.

Thanks, ordered a pack of 10 of them, any tips on soldering and desoldering these badboys, if nothing specific i will just watch a couple youtube videos

so best thing to do would be to check all the other relays if they have resistance? as far as i understood they should all read zero

Yea the unit was completly unplugged on my desk

its almost 5am over here, i have to go to bed, spring break is over soon, i really hope we can fix this before going back to uni

 

[TheseGoToEleven]

Thanks, ordered a pack of 10 of them, any tips on soldering and desoldering these badboys, if nothing specific i will just watch a couple youtube videos

so best thing to do would be to check all the other relays if they have resistance? as far as i understood they should all read zero

Yea the unit was completly unplugged on my desk

With the unit unplugged, all relays should have zero resistance between pins 2 & 3 and between pins 8 & 9.

For desoldering, it will be difficult with a simple solder sucker. If the legs were longer, you could cut the legs off on the top and then desolder from the bottom, but I don't think there is room to do that. Maybe Pucho knows a trick? I use a desoldering gun that makes it really easy, but they are expensive.